Fructose product



Patented Feb. 1, 1927.

UNITED STATES PATENT orr cs.

WILLIAM C. ABSEM, OF SCHENECTAIDY, NEW YORK, ASSIGNOR TO INDUSTRIALTECH- NICS CORPORATION, OF SCHENECTAD'Y, NEW YORK, A CORPORATION '01 NEWYORK! No Drawing. Original application filed July 12. 19 filed. November21, 1921, Serial No.

method is applied in its preferred form to pure inulin, preparedaccording to these processes, the final fructose sugar product obtainedis of unusual purity and is especiaL ly suitable for consumption as afood and also possesses unusually good keeping qualities.

Many attempts have hitherto been made to prepare a low cost sugar in theform of syrup, crystals, powder or the like, which could be substitutedfor sucrose (i. e., beet or cane sugar) for certain important uses suchas the preparation of soda syrups and soft drinks, the preservation offruits, the manufacture of confectionery, for general cooking purposes,for table use and similar purposes. But these attempts have been at mostonly partially successful. The nonsucrose syrups prepared hitherto forcommercial consumption, such as starch syrups, corn syrups, malt syrupsand the like, and all the solid, powdered and partially crystallineproducts prepared from similar sources, have failed to meet therequirements which sugar must have inorder to compete in the market withcane and beet sugar products for many important commercial purposes.

Thus, for example, none of ,the foregoing non-sucrose or sucrosesubstitute s rups are even approximately as sweet as t e syrups preparedfrom cane or beet sugar. Also such syrups are usually highly coloredand, therefore, cannot be used for many purposes for which ordinaryrefined cane or beet sugar syrupis employed and furthermore, certain ofthese syrups possess peculiar or variable flavors .which render themundesirable for many of the purposes mentioned. Thus in the preparationof carbonated or soft drinks it is desirable that the syrup used shallhave a definite and uniform flavor.

If the stock rnucrosn raonuc'r.

21, Serial no. 4:44.153. Divided and um application 516,886. RenewedOctober 4, 1926.

syrup or sugar from which the soda-syrupis prepared has a. peculiar orvariable flavor the natural or artificial flavoring material or extractis mixed to produce the finished soda-syrup.

Likewise in the production of confectioncry and culinary productsuniformity and purity of flavor of the'finished product is one of themost important requirements and therefore the sugar or syrup used mustnot possess a variable flavor and preferably should not have a highlypronounced flavor of its own.

Furthermore, uniformity of color of all of the above mentioned flnishedproducts is an important additional requirement and for this reasonstock syrups or su ars with .a pronounced or non-uniform or ojectionablc color of their own are not suitable for these very importantcommercial uses.

The various solid, powdered, and partially crystalline commercial formsof the non-s31; cross products hitherto produced do not meet theforegoing requirements and in adaition most of them have also thenudesirable property of absorbing moisture and becoming more or lesspasty so that they cannot be readily handled. Many of them also undergoobjectionable decompositions, when the attempt is made to keep them instorage for any considerable length of time or when they are employed incooking operations or in the manufacture of confectionery. I

The product of the present invention fulfills all the foregoingrequirements to an extraordinary degree and does not possess any of theabove mentioned objectionable qual1- ties and particularly it possessesthe property of sweetness in much greater degree than even cane or beetsugar. It is almost, if not quite. as freefrom objectionable coloredimpurities as is ordinary refined 'cane sugar syrup, so that it may beemployed for all ih purposes tor which ordinary waterhitg Cane sugarsyrup is employed. Furthermore,

' in syrup form it may be cooked or boiled without discoloration. Alsoin syrup form or in crystalline or solid form the fructosesugarfood-product of the present invention is resistant toward the attack ofcertain objectionable molds and bacteria and therefore possesses goodkeeping qualities.

Because of the ready availability 7 and cheapness of the raw simplicityand economy of the method by means of which the finished product of thepresent invention is produced, it can be manufactured at a very lowcost.

The methods hitherto commonly employed for preparing pure fructose frominulin involve complicated and expensive methods of re-crystallization,usually from alcohol. Such recrystallization or other purification ismade necessary because the older methods of hydrolysis yield"cliscoloredproducts or products which contaip hygroscopic, deleterious or otherwiseobjectionable impurities and which are therefore unsuited for many ofthe uses for which ordinary refined cane sugar products are employed.This is true even when highly purified inulin is used.

These impurities are very difficult to remove from the fructose bybleaching treatments, crystallization or similar methods and thereforeto obtain the fructose in even an approximately ure form by these oldermethods, it has een necessary to repeat the purification treatments agreat many times. The final yield of fructose so obtained is, therefore,so small that the cost of manufacturing by these older methods upon acommercial scale would be prohibitive.

The method of hydrolysis employed in producing the roduct of the resentinvention produces ructose of a high degree of purity directly from theinulin and thus avoids all the foregoing difficulties and disadvantages.It is based mainly upon a regulated hydrol sis of the inulin underdefinitely control ed conditions and in its preferred form thehydrolvsis is carried out;

with a selected acid and also with a definite range of concentration ofthe acid. One of the most important features of the improved methodreferred to is the adjustment of the time of hydrolysis to varyingconcentrations of acid and to the varying chemical nature of the acid.It has been found that highly advantageous results are obtainedby'stopping the hydrolysis at the end of a definitely determined periodof time. In determining this correct time of hydrolysis, account istaken, as already mentioned, not only of the chemical nature of the acidbut also of the concentration of the acid and also in certain instancesof the temperature and pressure.

By conducting the hydrolysis in this manner the inulin is readilyhydrolyzed completely into fructose of a very igh degree of puritymaterials used and the and a solution ofpu-re fructose is obtaineddirectly from the inulin solution without the necess1ty of resorting tothe olderelaborat'e and expensive methods of purification orcrystallization previously mentioned, Moreover, the fructose is obtaineddirectly in the form of a highly concentrated syrup and thus the cost ofevaporating the solution i: entirely avoided.

In other methods sometimes employed in the hydrolysis of inulin, a greatdeal of uncertainty has existed as to the optimum duration of thehydrolysis in order to obtain best yields of fructose. Theseuncertainties in the older methods referred to are due in large part tothe circumstance'that the intermediate hydrolytic products (if inulin,as well as the decomposition products, resulting from various sidereactions, all have properties which resemble those of fructose. If,therefore, one selects any convenient property of fructose and attemptsto determine the concentration of the fructose in the mixed solution bymeasurements of this property, the results'obtained will represent theresultant value of this property for all of the substances present.Thus, for example, since may of the hydrolytic and decompositionproducts are optically activeor possess the power to rotate the plane ofpolarized light, the measurement of this property, as the hydrolysisprogresses, does not always give a true measure of the concentration offructose in the solution but corresponds to the resultant rotation ofthe mixture of all the optically active substances present. Themeasurement of the reducing power of the solution, as a means'offollowing the progress of hydrolysis, leads to similar confusing resultsfor a similar reason, namely, that the various hydrolytic anddecomposition products each has a characteristic reducing power of itsown and, therefore, the reducing power of the mixed solu-- tionrepresents the resultant of that of all the substances present andcannotbe used as a measure of the concentration of any single one of theproducts present. It is, therefore, exceedingly diflicult to determinejust when the concentration of fructose in the mixed solution hasreached a maximum value.

' In the method employed in the present invention that as the hydrolysisof inulin progresses, the value of the negative rotation of polarizedlight. produced by the solution, usually increases at the l'ieginning ofthe hydrolysis and then later decreases. In other methods this firstmaximum negative value of rotation has frequently been taken to indicatethe highest obtainable concentration of fructose in the solution. I havediscovered, however. that this is not the case and that if thehydrolysis he continued after this first maximum negative rotation isreached, the negative value of the rotation theoretical rotation of thesolution, calculate'd. uponthebasis that all of the inulinpresent in thesolution is converted entirely into fructose. In this calculation thespecific rotation [ahoffructose is taken as minus ninety three degreesand the concentration ,of inulin in the solution is calculated from theweight of purified inulin dried to constant weight at 90 (1., which wasoriginally employed in making up the solution. In

this calculation the formula of inulin dried under these conditions 15taken as (1 ,11 0 Fructose exists in two tautomeric forms which areprobably stereoisomers, and are supposed to have the following formulascmoH on on omen p o p o no-d-n 1104 1-21 n-d-ou n-i z-mn n t l H t dinonHIGH a B The beta form, which is the ordinary crystalline form offructose in the pure state has a theoretical rotation of minus 135.5 at20 (3., but when'dissolved in waters portion of the beta form issupposed tochange over into the alpha form, which has not been isolatedas far as the applicant knows, but has a calculated rotation of 21 at 20C. The net effect after e uilibrium is reached is that the rotation ofte-mixture as a whole assumes an approximate value of about -93 at 20 C.-and this permanent or e uilihrium value will be referred to in theclaims as the maximum negative rotation.

The foregong methods furnish criteria for judging the extent of thehydrol sis of inulin' to fructose and therefore urnish means ofdetermining the total amount of impurities present in any given instanceunder the articular conditions of hydrolysis employe The total amount ofthese impurities corresponds to the difference between the percentage ofinulin which is completelyhydrolyzed to fructose and one hundredpercent. I have found that these impurities'are objectionable becausethey interfere with the subsequent crystallization of fructoseffromsolution and also because they im art increased hygroscopic propertiesto t e solid fructose obtained by crys- Similar y several dilfer-.

tallization or by evaporation of the hydrolyzed solution completely todryness, in accordance with methods such as that described in myco-opending application, Serial No. 369,537. Moreover, in many instancescertain of these impurities, particularlythose formed by thedecomposition of fructose after the latter has been formed, produceobjectionable discoloration of the solution and also discolor the solidfructose obtained therefrom. They also impart a variable orobjectionable flavor to the product.

Also I have found that there is an optimum'concentration for ;any givenacid, by

means of which substantially one hundred percent conversion of inulin tofructose can be obtained. A greater or smaller-concentration than thisoptimum concentration gives a poorer result. It has now been found thatto obtain a maximum conversion with a strong inorganic acid requires agreater optimum concentrationof acid than with an organic acid. Thus,for example.

the optimum concentration for hydrochloric acid is approximately fivehundredths normal, while with acetic acid the optimum concentration isonly about six thousandths normal. -W ith hydrochloric acid of thisoptimum concentration, the maximum conversion of inulin to fructose isreached in about five to ten minutes, whereas with acetic acid, of theabove given optimum concentration,

eight hours are required to produce a maximum conversion of the inulinto fructose.

7 Furthermore, I have discovered that the sion Wit 1 any given acidbears a certain definiteand fixed relation to the concentration of theacid and that for each kind of acid, keeping the inulin concentrationconstant,

this optimum time required for maximum conversion increases as theconcentration of .the acid diminishes, in such a way that thelogarithmof the reciprocal of the time is approximately proportional tothe logarithm of the normal concentration of the acid; In other words,the acid strength plotted against the reciprocal of, the correspondingtime gives an approximately straight line on logarithmic paper. Adifferent line is obtained, of course, for each kind of acid.Furthermore, I have discovered that the results btained with certainorganic acids sion of inulin to fructose. his relationship ssibleconver-v lOl) time required to reach a maximum. converres ill)

may be approximately expressed by means of the following equation:

Log. N=a log. riq+logx b in which N represents the normality of the acidin the usual sense, assuming that only the first hydrogen ion of theacid is active, while T is the time required for the highest possibleyield, expressed in hours and in which the constant a has a valuebetween about .7 and 1 and the constant 6 has a value varying betweenabout .007 and .03. The foregoing relationship between concentration andtime holds good for temperatures between about C. and 120 C. and forpressures of about one atmosphere. This relationship is not seriouslyaffected by changesin the original concentration of the inulin solutionfor concentrations greater than about eight percent by weight.

While it is desired that the scope. of the present invention shall notbe restricted by any unproven assumptions as to the exact chemicalnature of the reactions produced during the hydrolysis by certainorganic acids such as acetic, citric, maleic, malic, fumaric, lactic andtartaric acids on the one hand and by inorganic acids such ashydrochloric acid on the other hand, nevertheless, it is believed thatthe wide difference in their action may be best explained in thefollowing manner. The acid, it is thought, acts as a catalyst in thehydrolysis of inulin by virtue of the hydrogen ion concentration, whilethe failure of any given acid to produce a one hundred percentconversion under certain conditions or with certain concentrations isbelieved to be due to a condensing action of the undissociated moleculesof the acid or of the anion upon the products of the hydrolysis ofinulin and particularly upon the fructose. In other words, at each stageof the hydrolysis there seems to be two reactions going on which areopposed to each other in their effects, one reaction producinghydrolysis of inulin, probably through several intermediate stages, andanother reaction bringing about a decomposition or a condensation of thedifierent hydrolytic products and particularl of fructose.

I believe that there are tn'ee principal stages in the hydrolysis ofinulin and that two principal intermediate hydrolytic products areformed before fructose is produced, thus Inulincompound #1-compound #2fructose.

The reason, according to my belief, that the final stage has neverhitherto been completely attained, is that the hydrolysis has beenconducted under such conditions that the acid destroys the fructose or,the intermediate compounds forming hygroscopic subcifically, I may)stances such as levulosin, and also other decomposition products such ashumin, levulinic acid, formic acid, etc. It is my belief also that theseveral different maxima of polarization already-described, which areobtained during the course of the hydrolysis, correspond to maximumconcentrations of these principal intermediate hydrolytic compounds andI am convinced that this is the reason that the significance of thesedifferent maxima has hitherto been misunderstood resulting in a failureto obtain pure fructose directly from inulin as in the improved methodof the present invention.

- An example of my preferred method of carrying out the hydrolysis ofinulin is as follows:

Damp cakes of inulin prepared and purifled in accordance with themethods described in my copending application, Serial Number 424,459containing approximately 33%% inulin are stirred up thoroughly withsmall amountof a solution containing tartaric acid in an amountnecessary to make the solution .005 N when the cakes have been liquefiedby hydrolysis and assuming that the tartaric acid functions as amono-basic acid, only the first H ion being active. Spetake 100kilograms of inulin cake obtained y filter pressing or otherwise,containing 30-60% anhydrous inulin as determined b drying to constantweight at 90 C. This is put into an acid-proof vessel provided with anagitator and means for heating and'is heated to 100 C. with continuousstirring, whereupon it assumes a thin creamy consistency. Tartaric acid,gms. dissolved in a small amount of water, say one litre, is now addedand the heating continued for between two and three hours, or untilapproximately 100% of the inulin has been converted into fructose asdetermined by polariscopic tests as previously described. The resultingproduct is a practically pure slightly acid concentrated syrupy solutionof fructose. A smaller or larger amount of tartaric acid can be usedwith a corresponding change in the time as previously specified. Thesyrup may be used as such or evaporated or crystallized as for exampleas described in my co-pending applications Ser. No. 369,537 and Ser. No.424,459. I

It will be understood that I do not restrict myself to the articularproportions and conditions descrlbed in the preceding example, but I mayalter or vary these in accordance with the general characteristics andfeatures of my invention as previously described.

Among the principal advantages of the improved fructose food-product ofthe present invention, as compared with similar products hitherto known,are its greater stability especially toward heat, itsexceptionally oodkeeping qualities and in solid or, crysta line form its greater ireedomfrom a tendency to cake or become'pasty when exposed 'to a moist orhumid atmosphere. These special advantages of the new productparticularly its greater stability toward heat and its improved keepingqualities are due in large part, I believe, to the unusual purity of theproduct and to the nature and degree of its acidity. In some instances(and particularly where good keeping qualities are especially desired) 1have found that these advantageous properties can be increased by firsthydrolyzln the pure inulin with the limited amount 0 acid as specifiedand then, after the hydrolysis is completed and the product has cooledadding an additional' amount of acid either to the syrup or to the solidor crystalline product obtained therefrom by evaporation orcrystallization as, for example, by the method of evaporation and crstallization described in ications, Ser. No. 369,537

my co-pending app and Serial No. 424,459. Where the product is extendedfor consumption as a food itself or. as a constituent of a food, Iprefer to add an innocuous or edible acid such as citric acid andpreferably tartaric acid or an acid tartrate or the like.

In the manufacture of candy or confectionery and in many culinaryoperations where a sugar is employed, it is highly desirable that thesugar shall not decompose or darken in color. when cooked or heated andthe improved pure fructosev food-product of the present invention meetsthese requirements in a much more satisfactory manner than any similarproduct hitherto known.

When a pure fructose syrup, pre ared according to my invention, 18allows to stand for several days, it sometimes becomes slightl cloudwhich is objectionable, and I have liimnd t at this cloudiness is due tothe containing juices after clarification, unless special care is taken'to remove these last traces of calcium in some convenient manner. Iftartaric acid is used for hydrolysis this difficulty can be overcome bfiltering the syrup before bottling it, after it has been stored for afew days. A still better method of avoiding this difiiculty is tocarryout the hydrolysis by means of an organic acid which forms calciumsalt more soluble than calcium tartrate, such as lactic, malelc, lnalic,or fumaric acid.

This ap lication is a division of my application er. No. 484,153.

I claim:

l., A, new pure food product containing substantially pure fructose andan organic hydroxy acid. y

2. A new pure food-product containing substantially pure fructose andabout a fraction of a percent of a hydroxy organic acid. 3. A new purefood product containing substantially pure fructose and tartaric acid.4. A new pure food-product containing substantially pure fructose andabout a frac tion of a percent of tartaric acid.

5. A new pure food-product comprising a substantially colorless solutionof fructose and containing an organic hydroxy acid.

6. A new pure food-product comprising a'

